Timeouts can cause rollback, but rollback pays no attention to them if they happen while it is executing - it just ignores it - because the whole concept of rolling back a rollback is just plain silly.

I thought everybody knew that until I saw 40% wrong answers for this question.

I knew this had to be a trick question because I couldn't see why MS would add that command. As Tom said, rolling back a rollback is nonsense. Being April Fool's Day helped with my answer decision too.